Sheathed endoscope and sheath therefor

ABSTRACT

A sheathed endoscope has a flexible elongate insert part and a sheath that is removably fitted over the insert part. The sheathed endoscope comprises a distal end part that is provided at the distal end of the insert part, a distal end cover that is provided at the distal end of the sheath and that is removably fitted over the distal end part, and a lock device that is provided on the distal end cover so as to be engageable with the distal end part. The lock device is disengaged from the distal end part by deforming the distal end cover so that the lock device moves radially outward. A sheath for a sheathed endoscope is provided and is removably fitted over a flexible elongate insert part of the endoscope. The sheath comprises a flexible tubular member that is removably fitted over the insert part, a distal end cover that is connected to the distal end of the tubular member so as to be removably fitted over the distal end of the insert part, the cover being made of a shape-memory synthetic resin material that is restored to a previously memorized shape by heating it to a shape restoration temperature, and a lock device that is provided on the distal end cover.

This application is a division of application No. 07/630,896, filed Dec.20, 1990, now U.S. Pat. No. 5,257,617.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheathed endoscope which is designedso that an insert part of the endoscope is covered with a sheath thatcan be replaced with a new one each time the endoscope has been used inorder to prevent the transmission of bacteria and viruses from onepatient to another through the endoscope. The present invention alsorelates to a sheath that is used for the above-described sheathedendoscope.

The present disclosure relates to subject matter contained in Japanesepatent application Nos. 1-335534 and 1-335535 (both filed on Dec. 25,1989) which are expressly incorporated herein by reference in theirentirety.

2. Description of the Prior Art

A common sheath that is used for a sheathed endoscope comprises a tubeand a transparent distal end cover that is attached to the distal end ofthe tube, and that is removably fitted over an elongate insert part ofthe endoscope.

However, when such a sheath is merely fitted over the insert part of anendoscope, a gap may be produced between the distal end cover and thedistal end face of the insert part during use. In particular, a sheathedendoscope in which an end portion of a forceps inserting channel forinserting a tool for an endoscopic procedure, for example, a biopsyforceps, is connected to the distal end cover of the sheath involves theproblem that the distal end cover may be strongly pushed forward by theforceps inserting channel during use, resulting in a large gap betweenthe distal end cover and the distal end face of the insert part.

Such a sheathed endoscope has a viewing window and illuminating windows,which are provided at the distal end of the insert part, and both anobservation light and an illuminating light pass through the transparentdistal end cover. Accordingly, if a gap is produced between the distalend cover 251 of the sheath and the distal end face 261 of the insertpart of the endoscope, as shown in FIG. 9, part of the illuminatinglight that is emitted from the illuminating windows 262 enters theviewing window 263 after being reflected at the inner surface of thedistal end cover 251. In such a case, an intense flare or ghost mayappear in the observation field of view, thus degrading the observationcapabilities of the endoscope.

In order to prevent this problem, the distal end cover must be securedto the distal end of the insert part. However, the insert part of theendoscope must be formed as thin as possible with a view to minimizingthe pain given to the patient. It is therefore almost impossible tosecure the distal end cover to the distal end of the insert part bymeans, for example, of screws, because of the limited space. Inaddition, it would be troublesome to untighten and tighten screws foreach endoscopic procedure.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a sheathed endoscopewhich is designed so that the distal end cover of the sheath can bereliably locked to the distal end of the insert part of the endoscopeand can be removed therefrom with ease.

Another object of the present invention is to provide a sheath for theabove-described sheathed endoscope.

Other objects and advantages of the present invention will becomeapparent from the following detailed description of illustratedembodiments of the invention.

According to the present invention, there is provided a sheathedendoscope having a flexible elongate insert part and a sheath that isremovably fitted over the insert part, comprising: a distal end partthat is provided at the distal end of the insert part; a distal endcover that is provided at the distal end of the sheath and that isremovably fitted over the distal end part; and a lock device that isprovided on the distal end cover so as to be engageable with the distalend part. The lock device is disengaged from the distal end part bydeforming the distal end cover so that the lock device moves radiallyoutward.

In addition, there is provided a sheath for a sheathed endoscope that isremovably fitted over a flexible elongate insert part of the endoscope,comprising; a flexible tubular member that is removably fitted over theinsert part; a distal end cover that is connected to the distal end ofthe tubular member so as to be removably fitted over the distal end ofthe insert part, the cover being made of a shape-memory synthetic resinmaterial that is restored to a previously memorized shape by heating itto a shape restoration temperature; and a lock device that is providedon the distal end cover. The lock device is engageable with the distalend of the insert part at ordinary temperatures and is disengageabletherefrom when the distal end cover is restored to the memorized shape.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be more fully understood from the descriptionof preferred embodiments of the invention set forth below, together withthe accompanying drawings, in which:

FIG. 1 is a perspective view of a sheath according to a first embodimentof the present invention, which is removed from an insert part of anendoscope;

FIG. 2 is a sectional side view of the sheath according to the firstembodiment, which is assembled to the insert part of the endoscope;

FIGS. 3A and 3B are sectional views taken along the line III--III inFIG. 2;

FIG. 4 is a perspective view of a sheath according to a secondembodiment of the present invention, which is removed from an insertpart of an endoscope;

FIG. 5 is a sectional side view of the sheath according to the secondembodiment, which is assembled to the insert part of the endoscope;

FIG. 6 is a front view of the sheath according to the second embodiment,which is assembled to the insert part of the endoscope;

FIG. 7 is a sectional side view of the sheath according to the secondembodiment, which is being attached to the insert part of the endoscope;

FIGS. 8A and 8B are sectional front views of a distal end cover in thesecond embodiment of the present invention; and

FIG. 9 is a sectional side view of a sheath according to a prior art,which is assembled to an insert part of an endoscope.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1, which is a perspective view of a first embodiment of the presentinvention, shows an insert part 10 of an endoscope and the distal endportion of a sheath 20 that is removably fitted over the insert part 10.

The insert part 10 as a whole is formed from an elongate flexible tube.Theinsert part 10 is formed with a U-shaped groove 11 that extendsaxially over the entire length thereof in order to avoid interferencewith a channel tube 30.

A bendable portion 12 that is bendable by remote control is formed atthe distal end of the insert part 10. A distal end part 13 thatincorporates an objective optical system for observation is connected tothe distal endof the bendable portion 12.

The distal end face of the distal end part 13 is provided with a viewingwindow 14 for the objective optical system and illuminating windows 15where the emergent end of a light guide fiber bundle is disposed. Thewindows 14 and 15 slightly project to the same height from the distalend face of the distal end part 13.

The endoscope of this embodiment is an end-viewing endoscope andtherefore both of the optical axes of the observation light and theilluminating light are coincident with the axis of the insert part 10.

The distal end part 13 is formed from a cylindrical material. The upperside of the cylindrical material is provided with a U-shaped groove 11,and the left and right sides of the material are cut off straight todefine slant surfaces 19 that extend inwardly and gradually toward thelower side. In this embodiment, the slant surfaces 19 are formed inbilateral symmetry with each other so that the downward prolongations(as viewed in FIG. 1) of the slant surfaces 19 intersect each other.

Reference numeral 21 denotes a tubular member of the sheath 20 that isremovably fitted over the insert part 10 from the distal end thereof.The tubular member 21 is formed in the shape of a thin-walled cylinderusing aflexible and stretchable material, for example, silicone rubber.

A transparent distal end cover 22, made of a synthetic resin material,is connected to the distal end of the tubular member 21 in such a mannerthatno water will leak through the joint between the cover 22 and thetubular member 21. In use, the distal end cover 22 is removably fittedover the distal end part 13.

FIGS. 2 and 3A show the distal end portion of the sheath 20 which isattached to the insert part 10 of the endoscope. Reference numerals 16and17 denote an objective lens and an image guide fiber bundle,respectively, which are incorporated inside the viewing window 14 in thedistal end part

Since the distal end cover 22 of the sheath 20 has a cylindricalconfiguration, left and right spaces 18 are defined between the slantsurfaces 19 of the distal end part 13 and the distal end cover 22.

Reference numeral 30 denotes a channel tube that defines a forcepsinserting channel, which opens in the front face of the distal end cover22.

The distal end of the channel tube 30 is rigidly secured to the distalend cover 22. The channel tube 30 extends through the tubular member 21of thesheath 20 over the entire length thereof and is disposed in theU-shaped groove 11 in the insert part 10 of the endoscope.

Grooves 41 and 42 for click engagement are formed in the middle of thedistal end part 13. The groove 41 is provided in the bottom of theU-shaped groove 11, and the groove 42 is provided in a portion of thelower end of the distal end part 13 which is substantially on a straightline that bisects the angle between the two slant surfaces 19. On theother hand, the rear end portion of the distal end cover 22 is providedwith click pawls 43 and 44, which project inwardly so as to beengageable with the grooves 41 and 42, respectively.

Each of the click pawls 43 and 44 projects inwardly at right angles atthe inner end portion thereof (the left-hand side as viewed in FIG. 2)and forms a surface that gently slants toward the rear end.

Accordingly, when the sheath 20 is to be attached to the insert part 10of the endoscope, the distal end cover 22 of the sheath 20 is forcedonto thedistal end part 13 so as to cover the outer periphery of it. Inconsequence, the click pawls 43 and 44 are elastically deformed andhence temporarily expanded outwardly, and thereafter, the click pawls 43and 44 engage the grooves 41 and 42, as shown in FIGS. 2 and 3A. As aresult, thedistal end cover 22 is locked to the distal end part 13 in astate where the spring action caused by of the elastic deformation ofthe distal end cover 22 acts on the engagement between the click pawls43 and 44 and the grooves 41 and 42.

Thus, the tubular member 21 and the distal end cover 22 of the sheath 20isolate the insert part 10 of the endoscope from the externalenvironment,and the distal end face of the insert part 10, that is, thesurfaces of theviewing window 14 and the illuminating windows 15, arekept in close contact with the inner surface of the distal end cover 22.In this state, since the click pawls 43 and 44 are engaged with thegrooves 41 and 42, the sheath 20 cannot be removed from the insert part10 of the endoscope.

After the completion of an endoscopic inspection, the distal end cover22 is pinched with fingertips from the left and right sides thereoftoward the spaces 18, thereby elastically deforming the distal end cover22 into a vertically elongated shape, as shown in FIG. 3B.

As a result, the click pawls 43 and 44 move in radially outwarddirections in which they disengage from the grooves 41 and 42, so thatthe engagementbetween these members can be canceled.

However, when the distal end cover 22 is merely elastically deformedinto avertically elongated shape, the distal end cover 22 may bedeformed only atthe lower portion since it is more deformable than theupper portion. In such a case, the click pawl 43 may not completelydisengage from the groove 41 in the bottom of the U-shaped groove 11.

In this embodiment, however, the left and right side surfaces of thedistalend part 13 are formed into slant surfaces that extend inwardlyand gradually toward the lower side. For this reason, when the distalend cover 22 is pinched perpendicularly to the slant surfaces 19, asshown by the arrows A in FIG. 3B, force acts in a radially outwarddirection B about four fulcra 49 so as to raise the upper portion of thedistal end cover 22 as well as in a radially outward direction C.

Accordingly, the engagement between the click pawl 43 and the groove 41in the bottom of the U-shaped groove 11 can be canceled reliably. Inaddition, the engagement between the groove 42 and the click pawl 44 onthe lower portion of the distal end cover 22, which is more deformableinto an elongated shape, is simultaneously canceled.

Once the click pawls 43 and 44 are disengaged from the grooves 41 and 42bypinching the distal end cover 22 from both sides thereof, the sheath20 canbe readily removed from the insert part 10 of the endoscope andreplaced with a new one.

It should be noted that a click pawl may be provided only for one of theU-shaped grooves 41 and 42 and that the click pawls 43 and 44 are notnecessarily formed as integral parts of the distal end cover 22, but maybe provided as discrete parts. The distal end cover 22 need not betransparent throughout, but only at portions that face the observationandilluminating light paths.

According to the present invention, the distal end cover of the sheathcan be readily and reliably secured to the distal end of the insert partof the endoscope without a gap therebetween and yet the sheath can bereadilydisengaged and removed from the insert part simply by pinchingthe distal end cover by fingertips.

Since the transparent portion of the distal end cover is brought intoclosecontact with the distal end of the insert part when the cover issecured tothe insert part, it is possible to perform favorableendoscopic observationwithout the appearance of a flare or ghost in theobservation field of view.

FIG. 4, which is a perspective view of a second embodiment of thepresent invention, shows an insert part 110 of an endoscope and thedistal end portion of a sheath 120 that is removably fitted over theinsert part 110.

The insert part 110 as a whole is formed from an elongate flexible tube.The insert part 110 is formed with a U-shaped groove 111 that extendsaxially over the entire length thereof.

A bendable portion 112 that is bendable by remote control is formed atthe distal end of the insert part 110. A distal end part 113 thatincorporatesan objective optical system for observation is connected tothe distal end of the bendable portion 112. The distal end face of thedistal end part 113 is provided with a viewing window 114 for theobjective optical systemand illuminating windows 115 where the emergentend of a light guide fiber bundle is disposed. The windows 114 and 115slightly project to the same height from the distal end face of thedistal end part 113. The endoscope of this embodiment is an end-viewingendoscope and therefore both of the optical axes of the observationlight and the illuminating light are coincident with the axis of theinsert part 110.

Reference numeral 121 denotes a tubular member of the sheath 120 that isremovably fitted over the insert part 110 from the distal end thereof.Thetubular member 121 is formed in the shape of a thin-walled cylinderusing aflexible and stretchable material, for example, silicone rubber.A transparent distal end cover 122 is connected to the distal end of thetubular member 121 in such a manner that no water will leak through thejoint between the cover 122 and the tubular member 121. In use, thedistalend cover 122 is removably fitted over the distal end part 113.The distal end cover 122 is formed from a shape-memory synthetic resinmaterial that is restored to a previously memorized shape by heating itto a given shaperestoration temperature.

A shape-memory synthetic resin material is obtained by crosslinkingcertainsynthetic resin materials. It is possible to employ, for example,polynorbornene that is formed by a ring-opening polymerization ofnorbornene that is synthesized by the Dieis-Alder reaction from ethyleneand cyclopentadiene. The shape restoration temperature can be setrelatively arbitrarily, but in the application of the present inventionitis preferable to set the shape restoration temperature at about 50° to60° C.

In production, the distal end cover 122 is first formed by crosslinkinginto a memorized shape to which the distal end cover 122 is to berestoredupon heating (the memorized shape will be explained later).Next, the distal end cover 122 is made amorphous by heating it to atemperature above the melting point and is then deformed into a shapefor actual use, shown in FIGS. 4 to 6, and crystallized by cooling.Thus, the deformed state is fixed.

When the distal end cover 122 in the deformed state is heated to theshape restoration temperature, it is restored to the original shape(memorized shape), and this shape is maintained even when thetemperature lowers.

FIGS. 5 and 6 show the distal end portion of the sheath 120 which isattached to the insert part 110 of the endoscope. Reference numerals 116and 117 denote an objective lens and an image guide fiber bundle,respectively, which are incorporated inside the viewing window 114 inthe distal end part 113.

Reference numeral 130 denotes a channel tube that is formed with aforceps inserting channel 131 and air and water supply channels 132 and133, whichopen in the front face of the distal end cover 122. The distalend of the channel tube 130 is rigidly secured to the distal end cover122. The channel tube 130 extends through the tubular member 121 of thesheath 120 over the entire length thereof and is disposed in theU-shaped groove 111 in the insert part 110 of the endoscope. A nozzle134 is provided to direct the outlets of the air and water supplychannels 132 and 133 towardthe surface of the distal end cover 122 infront of the viewing window 114.

The outer peripheral surface of the distal end part 113 of the endoscopeisformed with, for example, three recesses 118 at respective positions.On the other hand, the inner peripheral surface of the distal end cover122 of the sheath 120 is integrally formed with projections 128 whichare engageable with the recesses 118 in the outer peripheral surface ofthe distal end part 113.

As shown in FIG. 5, each projection 128 projects inwardly at rightangles at the inner end portion thereof (the left-hand side as viewed inFIG. 5) and forms a surface that gently slants toward the rear end.

Accordingly, when the sheath 120 is to be attached to the insert part110 of the endoscope, the distal end cover 122 of the sheath 120 isforced onto the distal end part 113 so as to cover the outer peripheryof it (seeFIG. 7). In consequence, the projections 128 are elasticallydeformed and hence temporarily expanded outwardly, and thereafter, theprojections 128 engage the recesses 118, as shown in FIG. 5. As aresult, the distal end cover 122 is locked to the distal end part 113 ina state where the springaction caused by the elastic deformation of thedistal end cover 122 acts on the engagement between the projections 128and the recesses 118.

In the state that is shown in FIG. 5, the tubular member 121 and thedistalend cover 122 of the sheath 120 isolate the insert part 110 of theendoscope from the external environment, and the viewing window 114 andthe illuminating windows 115 are kept in close contact with the innersurface of the distal end cover 122. At ordinary temperatures, thedistal end cover 122 maintains the state that is shown in FIG. 5 andhence the projections 128 cannot disengage from the recesses 118, sothat the above-described state is maintained.

However, since the distal end cover 122 is formed from a shape-memorysynthetic resin material, as stated above, it can be restored to theoriginal shape (memorized shape) by heating it to a temperature abovethe shape restoration temperature with hot water or hot air after thecompletion of an endoscopic inspection.

There is no particular restriction on the original (memorized) shape ofthedistal end cover 122. It is possible to employ any shape that allowsthe projections 128 to disengage from the recesses 118, for example, ashape in which only those portions where the projections 128 are locatedprojectoutwardly, as shown in FIG. 8A, or a shape in which the wholedistal end cover 122 has a greater diameter than that of the deformedshape, as shownin FIG. 8B.

Once the projections 128 are disengaged from the recesses 118 by heatingthe the distal end cover 122, the sheath 120 can be readily removed fromthe insert part 110 of the endoscope and replaced with a new one.

It should be noted that the projections 128 are not necessarily formedas integral parts of the distal end cover 122, but may be provided asdiscrete parts. The distal end cover 122 need not be transparentthroughout, but only at portions that face the observation andilluminating light paths.

According to the present invention, the distal end cover of the sheathcan be readily and reliably secured to the distal end of the insert partof the endoscope so that the distal end cover will not be displaced, andyet the sheath can be readily disengaged and removed from the insertpart simply by heating the distal end cover.

Since the transparent portion of the distal end cover is brought intoclosecontact with the distal end of the insert part when the cover issecured tothe insert part, it is possible to perform favorableendoscopic observations without the appearance of a flare or ghost inthe observationfield of view.

While the invention has been described by reference to specificembodimentschosen for purposes of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

I claim:
 1. A sheath for a sheathed endoscope that is removably fittedover a flexible elongate insert part of said endoscope, comprising;aflexible tubular member that is removably fitted over said insert part;a distal end cover that is connected to the distal end of said tubularmember so as to be removably fitted over the distal end of said insertpart, said distal end cover being made of a shape-memory synthetic resinmaterial that is restored to a previously memorized shape by heating itto a shape restoration temperature; and lock means that is provided onsaid distal end cover, said lock means engaging the distal end of saidinsert part at ordinary temperatures and disengaging therefrom when saiddistal end cover is restored to the memorized shape.
 2. A sheath for asheathed endoscope according to claim 1, wherein said shape-memorysynthetic resin material is polynorbornene that is formed by aring-opening polymerization of norbornene that is synthesized by theDieis-Alder reaction from ethylene and cyclopentadiene.
 3. A sheath fora sheathed endoscope according to claim 1, wherein said distal end coveris transparent at at least a portion thereof that faces an optical pathof said endoscope, said transparent portion of said distal end coverbeing brought into close contact with the distal end face of said insertpart when said lock means is engaged with said distal end part.
 4. Asheath for a sheathed endoscope according to claim 1, wherein said lockmeans is formed as an integral part of said distal end cover.
 5. Asheath for a sheathed endoscope according to claim 1, wherein a channeltube for inserting a tool for an endoscopic procedure extends throughsaid tubular member over substantially the entire length thereof, oneend of said channel tube being connected to said distal end cover.